Phenotyping of TH9 Cells in Cytomegalovirus-reactivated Kidney Transplant Recipients

Abstract

Human cytomegalovirus (HCMV) is a frequent complication in kidney transplant recipients (KTRs), often impacting immune regulation. T_H9 cells, a subset of CD4⁺ T cells, are characterized by their secretion of interleukin-9 (IL-9). This study aimed to analyze the phenotypic profile of T_H9 cells and their associated cytokine expression in KTRs, and to evaluate mRNA levels of IL-4 and transforming growth factor-β (TGF-β), key cytokines involved in T_H9 differentiation.

Ten HCMV⁺ and 10 HCMV⁻ KTRs, along with 10 age- and sex-matched healthy controls, were enrolled. HCMV viral load was quantified using TaqMan real-time polymerase chain reaction. Flow cytometry was used to assess surface markers (CCR6⁺CCR4⁻IL-4Rα⁺CD4⁺) and intracellular IL-9 expression in T_H9 cells. Gene expression levels of IL-4 and TGF-β were also assessed.

Surface staining revealed a significantly higher frequency of CD4⁺CCR4⁻ and CD4⁺CCR6⁺ T cells in HCMV⁻ KTRs compared to HCMV⁺ patients. Conversely, the overall frequency of CD4⁺ T_H9 cells was elevated in HCMV⁺ KTRs. Intracellular staining demonstrated a significant increase in CD4⁺IL-9⁺ and CD4⁺IL-4Rα⁺ T cells in the HCMV⁺ group. Additionally, mRNA expression levels of IL-4 and TGF-β were markedly higher in HCMV⁺ KTRs than in HCMV⁻ counterparts.

These findings suggest a potential role for T_H9 cells and their signature cytokine IL-9 in the antiviral immune response in KTRs. While T_H9 cells may contribute to HCMV-related immune modulation, further research is needed to fully elucidate their protective mechanisms against viral infections.